Combustion apparatus and methods

ABSTRACT

A combustion apparatus is described having a generally elongated combustion container with a longitudinal axis, a proximal end, an exhaust end spaced axially forward from the proximal end, a proximal end wall, an exhaust end wall, and an all-around sidewall extending between the end walls and about the longitudinal axis. The end walls and sidewall substantially define a combustion chamber. The apparatus also includes a combustion chamber exhaust positioned on the exhaust end, a fuel-air delivery system positioned to direct fuel into the combustion chamber, and an air inlet located generally tangentially on the sidewall to direct air flow generally tangentially into the chamber and induce swirl about the longitudinal axis.

The present application claims the benefit of U.S. ProvisionalApplication Ser. No. 61/403,290, filed on Sep. 12, 2010 (pending). Thedisclosure of the previously filed provisional application is herebyincorporated by reference for all purposes and made a part of thepresent disclosure.

This invention was made with government support under Contract Nos. ONRN00014-10-C-0334 and ONR N00014-09-C-0121 awarded by the Office of NavalResearch. The government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a fuel combustion method andan apparatus for performing same. More particularly, the inventionrelates to an apparatus and/or method for providing a generallyuniformly volume distributed combustion, and further, an improvedapparatus and/or method of mixing for uniformly volume distributedcombustion.

2. Description of Related Art

It was arguably not until the late 1970s and early 1980s, as a result ofthe first and the second energy crisis, that research and developmentactivities began to seriously focus on improving energy efficiency.Similarly, in the same time period, industry began to truly recognizethe need for eliminating noxious pollutants such as nitrogen oxides,mostly due to concerns over human health and concern for theenvironment.

To achieve these goals, the combustion temperature must be less thanthat at which nitrogen oxidizes. On the other hand, the combustiontemperature must be high enough for complete combustion with carbonmonoxide totally burnt. Therefore, the optimal combustion temperaturemust be around 1100° C. For combustion to occur at the optimaltemperature, fuel and an oxidizer must be finely mixed and preheatedthroughout the entire combustor volume. Although uniformly distributed(flameless) combustion was discovered circa 1911, it was not untilrecently that uniformly distributed combustion (flameless oxidation) hasbecome a focus of industrial research.

In flameless combustion, ignition occurs and progresses with generallyno visible or audible signs of a flame that is usually associated withburning. As early as 1989, it was found that combustion in a furnacecould be sustained even with an extremely low concentration of oxygen,if the combustion air was sufficiently preheated. Particularly, duringexperiments with a self-recuperative burner, it was observed that atfurnace combustion temperatures of about 1000° C. and an air preheattemperature of about 650° C., no flame was visible and no ultravioletsignal was detected. Nevertheless, the fuel was totally burnt, andcarbon monoxide as well as nitric oxide content of the exhaust was foundto be extremely low.

Conventionally, to initiate flameless combustion, preheated oxidizingair and gas fuel is fed into a combustion chamber at relatively highinjection speeds. The geometry of the combustion chamber and the highinjection speed of the fuel-air mixture create large internalrecirculation of the combustion mixture. Once the recirculation issufficient, the combustion becomes distributed throughout the volume ofthe combustion chamber and the flame is no longer visible. Further, asan application of such a principle, nitric oxide emission can be reducedthrough the dilution of the combustion air with the circulated burnedgas in the furnace. Dilution of the combustion air can reduce the oxygencontent of the oxidizer, which decreases temperature fluctuations in thecombustion chamber as well as the mean temperature, resulting in lowamounts of nitric oxide emission.

Recognizing the potential benefits of flameless combustion, the industryhas attempted to develop various types of combustion chambers whichsupport flameless combustion. For example, U.S. Pat. No. 6,796,789 byGibson et al., entitled “Method to Facilitate Flameless CombustionAbsent Catalyst or High-Temperature Oxidant” describes an oval-shapedcombustion chamber configured to circulate gas fuel with flue gas andcombustible air. U.S. Pat. No. 5,340,020 by Manus et al., titled “Methodand Apparatus for Generating Heat by Flameless Combustion of a Fuel in aGas Flow” describes a combustion apparatus, which utilizes a catalystfor producing the flameless combustion. U.S. Pat. No. 6,826,912 B2,issued on Dec. 7, 2004 by Y. Levy et al., entitled “Design of AdiabaticCombustors” describes a gas turbine combustion chamber, to producehigh-pressure gases for the turbine. The combustion chamber has aprimary combustion zone containing a substantially vitiated-air zoneinto which the fuel is injected. The primary air inlet is positioned anddirected to produce an internal recirculation that generates a ring-likevortex within the primary zone, thereby providing the vitiated-air zoneand maintaining therein a state of flameless oxidation.

U.S. Pat. No. 5,839,270 by Jirnov et al., entitled “Sliding-Blade RotaryAir-Heat Engine with Isothermal Compression of Air” describes aparticularly efficient combustion chamber originally configured for usewith the sliding-blade rotary air-heat engine. The Jirnov “vortex”combustion combined with a straight-flow pre-combustion chambersuccessfully solved problems associated with multi-fuel operation with ahigh completeness of combustion over the wide range of the coefficientof air concentration, while producing a substantial drop in toxicity ofthe exhaust gases. The combustor was also characterized by providing asimplified combustor design and ease of fabrication, high thermal aswell as volumetric efficiency, while being able to employ various typesof combustible hydrocarbon gas or liquid fuel.

Yet another combustion apparatus suitable for flameless combustion isdescribed in U.S. patent application Ser. No. 12/774,576, filed May 5,2010, and entitled “Apparatus and Methods for Providing UniformlyDistributed Combustion of Fuel”, (which application is assigned to acommon assignee of the present application and includes at least onecommon applicant/inventor). The disclosure of U.S. patent applicationSer. No. 12/774,576 is incorporated herein by reference for all purposesand made a part of the present disclosure. In this previously filedapplication, a combustion chamber is described as including aprecombustion chamber in addition to a main combustion chamber. Thepre-combustion chamber provides delivery of a super-rich fuel and airmixture, ignition, and/or partial combustion and decomposition of heavyand low grade fuels. In operation with the Jirnov engine, prior toentering the pre-combustion chamber, the combustion air is preheated byexhaust gases and then, upon entry, heating coils in the pre-combustionchamber further heat the air. Heated fuel is also injected into thepre-combustion chamber prior to entry into the main vortex combustionchamber.

To further facilitate uniformly volume distributed combustion of fuel,the pre-combustion chamber in this previous application provides atleast one air injection inlet port positioned to induce a first stagevortex in the pre-combustion chamber. Further, the pre-combustionchamber is interfaced with the main combustion chamber to induce asecond stage vortex in the mian combustion chamber. Specifically, theentry of the fuel-air mixture into the main vortex combustion chamber issuch that a very large swirl is created which helps ensure propermixture and a substantially uniform combustion within the combustionchamber. The main vortex Combustion chamber may also be equipped with anelongated combustion exhaust conduit. The conduit extends from theexhaust of the combustion chamber to the opposite end of the chamber.The combustion exhaust conduit provided therefore is a physical orstructural barrier between the inlet to the main vortex combustionchamber and its exhaust.

In recent years, due to the cost of fuel and due to concern for theenvironment, there has been a high interest in the use of bio-fuels.Bio-fuels can include solid, liquid or gas fuel derived from recentlyexpired biological material. Theoretically, bio-fuel can be producedfrom any biological carbon source, the most common of which includesplants as well as plant-derived materials. The bio-fuel industry isexpanding in Europe, Asia and the Americas. The most common use forbio-fuels is as liquid fuels for automotive transport. However, there isalso a desire within the industry to use bio-fuels to generate steamand/or electricity. Bio-diesel is the most common bio-fuel in Europe,and is becoming more popular in Asia and America. Biodiesel can beproduced from oils or fats and forms into a liquid similar incomposition to petroleum diesel.

For example, bio-diesel production can result in glycerol (glycerin) asa by-product at one part glycerol for every 10 parts biodiesel. This hasresulted in saturation in the market for glycerol. Accordingly, ratherthan being able to sell the glycerol, many companies have to pay for itsdisposal. Sources indicate that the 2006 levels of glycerol productionwere at about 350,000 tons per annum in the USA, and 600,000 tons perannum in Europe. Sources further indicate that such levels will onlyincrease as biodiesel will become more popular as a homegrown energysource and as Europe implements EU directive 2003/30/EC, which requiresreplacement of 5.75% of petroleum fuels with bio-fuel, across all memberstates by 2010. Therefore, inventors recognized the need for anapparatus as well as methods of economically disposing of glycerin orother byproducts in an environmentally friendly and energy efficientmanner.

The applicants also recognize that, although considered a waste productof biodiesel fuel production, byproducts, such as glycerin, havesignificant energy delivery potential. Glycerin, however, along withsome other forms of waste/bio-fuels, has characteristics which must beovercome in order to employ them as a fuel source. Conditions requiredfor efficient combustion of glycerin and other waste/bio-fuels includepreheating, fuel fine atomization, fast and fine mixing with oxidizer aswell as sufficient residence time in a combustion chamber. Therefore,recognized by the applicants is the need for an apparatus and methodsfor economically and efficiently burning such heavily viscouswaste/bio-fuels in a combustion chamber to produce an exhaust which canbe utilized as an energy source.

Further recognized by the applicants is the need for such an apparatusand methods which can provide uniform volume-distributed oxidation tothereby decrease harmful emissions and increase energy efficiency. Tothis end, it is also desirable to provide improved means and apparatusfor uniform volume distributed oxidation and uniform flamelesscombustion.

SUMMARY OF THE INVENTION

In view of the foregoing, embodiments of the present inventionadvantageously provide an apparatus and methods for economically andefficiently burning gaseous and liquid fuels, as well as viscouslow-grade bio-fuels. Embodiments of the present invention alsoadvantageously provide an apparatus a combustion chamber configured toprovide a uniform volume distributed fuel-oxidizer mixture to therebydecrease nitric oxide emissions and increase energy efficiency.Embodiments of the invention also include related methods of operatingsame, and more particularly, combustion methods including advantageouslyorganizing flows within a chamber to enhance mixing and/or heattransfer. Embodiments of the present invention provide an apparatus andmethods which improve upon the Jirnov vortex combustion chamber andprecombustion chamber and methods described in U.S. Pat. No. 5,839,270by Jirnov et al., entitled “Sliding-Blade Rotary Air-Heat Engine withIsothermal Compression of Air” and the U.S. patent application Ser. No.12/774,576, filed May 5, 2010, titled “Apparatus and Methods forProviding Uniformly Distributed Combustion of Fuel.”

As used herein, the term “fine mixing” is a term known by those skilledin the art, and means that the distance between an oxidizer molecule anda fuel molecule become close or substantially close to the free path ofmolecules. The term “fast mixing” is also a term in the art and meansthat the time of mixing is significantly shorter than the residence time(axial length dimension/axial velocity). The mixing time is generallyunderstood to be equal to a dimension scale of eddies divided by theturbulence velocity (difference in two magnitude of velocities). It isdesirable for the mixing time to be substantially smaller small than thecombustion time (which is a function of temperature, pressure etc.). Inother, more specific descriptions of aspects of the invention providedhere, the term mixing may refer also to facilitating and enhancing theheat transfer between “mixed’ or distributed constituents of thecombustion chamber.

In the pursuit of desirable combustion properties, including stable andsubstantially complete fuel burning with low levels of harmfulemissions, it is desirable to generate high speed counter flows, andfine scale Karman eddies so as to promote fast and fine mixing ofcombustion constituents. As further understood by applicants, fast andfine mixing, including preheating, facilitates uniformly volumedistributed oxidation and uniform flameless combustion. To achieve thesespecific conditions, applicants sought to provide a combustor and methodthat entail the specific organization of advantageous flows preceding orsimultaneous with combustion.

In one aspect, a combustion apparatus is disclosed having a generallyelongated combustion container. The container has a longitudinal axis, aproximal end, an exhaust end spaced axially forward from the proximalend, a proximate end wall, an exhaust end wall, and an all-aroundsidewall extending between the end walls and about the longitudinalaxis, the end walls and sidewall substantially defining a combustionchamber. The apparatus further includes a combustion chamber exhaustpositioned on the exhaust end, a delivery system positioned to directfuel into the combustion chamber for combustion, and an air inletlocated generally tangentially on the sidewall to direct air flowgenerally tangentially into the chamber and induce swirl about thelongitudinal axis. In a preferred embodiment, an outside casing isprovided about the combustion container and spaced circumferentiallyoutward from the container to define an air annulus therebetween. Thecasing is equipped with an outer air inlet that communicates an externalair supply with both the annulus and the air inlet into the combustorchamber. Accordingly, the air annulus can direct air flow toward theproximate end and along the outside of the container thereby exchangingheat with the side walls of the container and more preferably, directinghot air to the proximate end and in the vicinity of a fuel-air deliverysystem associated with the combustion chamber. In this way, the annulusserves to cool the side walls and recirculate the heat loss back intothe combustion chamber.

In another aspect, a method of combustion is provided. The methodentails providing an elongated combustion container having alongitudinal axis, a pair of axially spaced apart end walls generallydefining a proximate end and a distal end, a sidewall extending betweenthe end walls, and an exhaust opening in the distal end. Fuel isdelivered into the chamber at the proximal end and tangential air flowis introduced into the combustion chamber to induce swirl flow about thelongitudinal axis. The swirl flow further induces meridional circulationin the combustion chamber, including circulatory regions and flowthrough regions exiting the exhaust opening. Furthermore, combustion isinitiated in the combustion chamber, which includes exhausting hot gasesthrough the exhaust opening.

In yet another aspect, a fuel and air delivery system is disclosedhaving a radial air swirler and a fuel nozzle. The air swirler includesa swirl chamber positioned about a swirl axis, a radial inlet forintroducing rotational air flow into the swirl chamber, and a centralopening positioned to receive swirling flow from the chamber. The fuelnozzle is directed axially through the central opening of the swirler,and wherein the air swirler further includes a nozzle outlet in fluidcommunication with the central opening and having an all aroundforwardly diverging sidewall for directing a diverging annular swirlflow outward.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the presentinvention may be understood in more detail, a more particulardescription of the invention briefly summarized above may be had byreference to the embodiments thereof which are illustrated in theappended drawings that form a part of this specification. It is to benoted, however, that the drawings illustrate only various exemplaryembodiments of the invention and are therefore not to be consideredlimiting of the invention's scope as it may include other effectiveembodiments as well.

FIG. 1 is a longitudinal cross-sectional view of a combustion apparatus,according to the present invention;

FIG. 2 is a lateral cross-sectional view along line 2-2 in FIG. 1;

FIG. 3 is a lateral cross-sectional view along line 3-3 in FIG. 1;

FIG. 4 is a detailed side view of a fuel-air mixture delivery system inFIG. 1;

FIG. 4A is a simplified side view illustration of the fuel-air deliverysystem in FIG. 4 further illustrating a local circulation regiongenerated by the system, according to the present invention;

FIG. 5 is a perspective view of an air swirler according to the presentinvention;

FIG. 6 is a graphical diagram illustrating fuel and air and flowcharacteristics proximate the fuel-air delivery system in FIG. 4 duringoperation, according to the present invention;

FIG. 7 is a simplified schematic of the combustion apparatus in FIG. 1and circulatory flows generated therein, according to the presentinvention;

FIG. 7A is a simplified representation of the results of numericalsimulations describing meridional motion in the combustion apparatus inFIG. 7;

FIGS. 8A-8E are simplified illustrations of particle swirl trajectoriesgenerated in the combustion apparatus in FIG. 7 during operation,according to the present invention;

FIG. 9 is a simplified schematic of an alternative combustion apparatusand circulatory flows generated therein, according to the presentinvention;

FIG. 9A is a simplified representation of results of numericalsimulations describing meridional motion in the combustion apparatus inFIG. 9;

FIG. 10 is a simplified schematic of circulatory flows generated insidea combustion apparatus, according to an alternative embodiment of thepresent invention;

FIG. 10A is a simplified representation of results of numericalsimulations describing meridional motion in the combustion apparatus inFIG. 10;

FIG. 11 is a simplified side view illustration of an alternate combustorapparatus in the form of a burner, according to the present invention;

FIG. 12 is a simplified schematic of yet another alternative embodimentof a combustion apparatus, and circulatory flows generated therein,according to the present invention;

FIG. 13A is a perspective view of a combustion apparatus according toyet another alternative embodiment of the present invention;

FIG. 13B is a side view of the combustion apparatus in FIG. 13A;

FIG. 13C is a rear view of the combustion apparatus in FIG. 13A;

FIG. 13D is a longitudinal cross-sectional view of the combustionapparatus in FIG. 13A;

FIG. 14A is a perspective view of a combustion liner and transitionpiece, according to the present invention;

FIG. 14B is a side view of the combustor components in FIG. 14A;

FIG. 14C is a longitudinal cross-sectional view of the combustorcomponents in FIG. 14B;

FIG. 14D is a rear view of the combustor components in FIG. 14A;

FIG. 14E is a front view of the combustor components in FIG. 14A;

FIG. 14F is a lateral cross-sectional view across line 14F-14F in FIG.14B;

FIGS. 15A and 15B simplified illustration of fluid dynamics proximatemultiple fuel-air delivery systems as implemented in the combustionapparatus of FIG. 13, according to the present invention;

FIG. 16A is an axial end view of an alternate combustion apparatus,according to the present invention;

FIG. 16B is a detailed cross-sectional view of a transition pieceoperable with the combustion apparatus in FIG. 16A;

FIG. 17A is a simplified representation of a combustion apparatusaccording to the invention; and

FIG. 17B is a simplified representation of an alternate embodiment ofthe combustion apparatus.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference tothe accompanying drawings, which illustrate the various exemplaryembodiments of the present invention. This invention may, however, beembodied in many different forms and should not be construed as limitedby the illustrated embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough aswell as complete and will fully convey the scope of the invention tothose skilled in the art and the best and preferred modes of practicingthe invention.

FIGS. 1-17 depict various combustion systems, components of combustionsystems, and various applications of the combustion systems, embodyingor exemplifying one or more aspects of the present invention. In onerespect, a combustion apparatus according to the invention and itsvarious applications represent improvements to the vortex combustionchamber and the precombustor and main combustor configurations describedabove. More specifically, the combustion apparatus and its method ofoperation achieves generally uniformly volume distributed oxidation andfurther, improves mixing of fluids (e.g., fuel, air, flue gas, and othercombustion constituents) in the combustion apparatus. In furtheraspects, the combustion apparatus and method achieve fast and finemixing of fluids for combustion. The inventive combustion apparatus canachieve flameless combustion conditions at the exit, substantiallycomplete combustion, and very low levels of nitric oxide (NOx) andcarbon monoxide (CO) emissions. Embodiments of the invention are,therefore, well suited for use with turbines and heating systems.Specific applications of the combustion apparatus according to theinvention include those utilizing a conventional liquid fuel such as jetpropellant, diesel, kerosene, or gasoline, or a gaseous fuel, such ashydrogen, CO, or carbohydrate. Other applications may utilize theburning of a waste fuel, such as glycerol (glycerin) and emulsifiedheavy oil (with water) fuels.

Exemplary Combustion Apparatus and Method

Referring first to FIGS. 1-5, a combustion apparatus 7, according to anembodiment of the present invention, features a generally cylindricalouter casing or housing 13 defined partly by a longitudinal axis YY. Theouter housing 13 includes an all-around sidewall 15 positioned about theaxis YY and extending between a pair of end walls 17, 19. In embodimentsdescribed herein, the outer housing 13 (i.e., the combustion apparatus7) is operationally engaged with a fuel supply (fuel pipe 21) at or nearthe proximal end wall 17, a transition piece at the opposite or distalend wall 19, and a high pressure air source, such as a compressor, atthe sidewall 15.

Referring to FIG. 1 specifically, the proximal end wall 17 is positionedon the left side of the Figure while the distal end wall 19 is spacedaxially to the right and across the axial length of the outer housing13. The end walls 17, 19 are preferably arranged in mutual parallelrelation and generally perpendicular to the longitudinal axis YY.

In preferred embodiments, the combustion apparatus 7 exhausts hot fluegases at the distal end and through a centrally located exhaust opening25. An exhaust pipe 23 extends though the distal end wall 19 and engagesthe exhaust opening 25 to receive the high pressure, hot flue gases. Theexhaust pipe 23 communicates the gases to a transition piece, turbine,nozzle, or other component, as required by the specific application. Insome of the descriptions provided herein, components, fluids, orprocesses described at or about the distal end wall 19 may be referredto as being forward or downstream of components or fluids described asnear the proximal end wall 17. The distal side or end of the combustionapparatus 7 may also be referred to as the exhaust or exhaust end.

The combustion apparatus 7 also includes an elongated, preferablycylindrical combustor liner (or combustion container) 31 having adiameter less than that of the outer housing 13. The combustor liner 31is positioned centrally within the outer housing 13 about thelongitudinal axis YY, thereby defining an elongated cavity or combustionchamber 33. The preferably cylindrical combustor liner 31 is furtherdescribed as including all around sidewalls 35 that extend axiallybetween a substantially enclosed proximal end wall 37 and a partiallyopen distal end wall 39. The distal end wall 37 is located substantiallyadjacent the distal end wall 19 of the housing 13, such that thecentrally located exhaust opening 25 goes through both end walls 19, 39.The proximal end wall 37 is preferably spaced axially forward of theproximal end wall 17 of the outer housing 13 to define a cylindricalspace 9 therebetween. In preferred embodiments, the proximal end wall 37and the area thereabout are utilized for receiving primary air, liquidor gaseous fuel, and delivering the desired fuel-air mixture forcombustion. The cylindrical space 9 accommodates some of the componentsand facilitates some of the processes involved, as further describedbelow.

The combustor liner 31 is also sized such that when the combustor liner31 is centered within the housing 13, an annulus 41 of desired gap widthis provided between the outer housing 3 and the combustor liner 31. Asshown in FIG. 1, the annulus 41 extends circumferentially about theliner 31 and also axially past each end wall 37, 39 and into thecylindrical space 9. The outer housing 13 is further equipped with anair inlet opening 29 in the sidewall 15 and an air inlet pipe 27 thatengages the inlet opening 29. The air inlet pipe 27 delivers pressurizedair from the external compressor into the annulus 41 and the annulus 41communicates the pressurized air throughout the outside of the liner 31,including the cylindrical space 9.

Pressurized air is also delivered to the combustion chamber 33. In theembodiment depicted by FIGS. 1-2, the sidewall 35 of the liner 31includes a tangential opening or inlet 43 that corresponds with the airinlet opening 29 of the outer housing 13. The opening 43 is spaceddirectly inwardly from the air inlet opening 29 and is positionedtangentially on the sidewall 35. The opening 43 fluidly communicates,therefore, with the air inlet pipe 27 and allows injection of highpressure air into the combustion chamber 33. Due to the location of theopenings 29, 43, high pressure air enters the combustion chamber 33generally tangentially and at relatively high velocity, therebyfacilitating swirl flow about the axis YY. Furthermore, the air inletpipe 27 and opening 43 deliver high pressure, fresh air into thecombustion chamber 33 and induces commencement of swirl flow at an axiallocation substantially near the exhaust 25 (i.e., well past the axialmidpoint of the combustion chamber 33).

The configuration in FIG. 1 contrasts with that of previously describedcombustors. In the earlier-described combustor of U.S. patentapplication Ser. No. 12/774,576, the pressurized air inlet is alsolocated axially and physically close to the exhaust. A combustionexhaust conduit is positioned around the exhaust, however, to provide aphysical barrier directly between the inlet and the exhaust and toensure that the fresh air inflow travels at least substantially theaxial length of the combustor chamber before exiting the chamber.

Fuel-Air Delivery System

Referring specifically to FIGS. 3 and 4, the proximal end wall 37 of thecombustor liner 31 supports an arrangement for delivering fuel and airfor combustion purposes (hereinafter, fuel-air nozzle or fuel-airdelivery system 45). In accordance with a further aspect of theinvention, operation of the fuel-air delivery system 45 generates localcirculation regions that serve as flame holders and help to quicklyvaporize droplets of liquid fuel. The fuel-air mixture delivery system45 may be described as including a disc-shaped swirler nozzle or swirler47 and a fuel nozzle 49 operable with the swirler 47 to deliver fuel andair into the combustion chamber 33. Connected with the fuel pipe 21, thefuel nozzle 49 delivers a highly atomized jet or spray of liquid fuelinto the local circulation region and the rest of the combustion chamber33 (or a gaseous fuel in other applications). The fuel-air deliverysystem 45 may also be described as including an igniter (not shown inthe Figures for this embodiment) positioned proximate the 10 localcirculation region LCR and/or the fuel nozzle 49 to initiate combustion.

The primary components of the swirler 47 include a pair of open-centeredcircular discs or plates 53 that are attached to the proximal end wall37 and about a circular opening in the end wall 37 and a swirl axis ZZ(which is preferably coincidental with axis YY). Independent of the endwall 37, the circular plates 53 are spaced apart in mutually parallelrelation to define a swirl chamber and a converging air paththerebetween. A plurality of radially arranged guide vanes are supportedbetween the plates 53 just inside of the periphery of the plates 53. Theradial guide vanes 55 are spaced apart and similarly angled to drawprimary air into the swirl chamber along generally the same tangentialdirection (relative to swirl axis ZZ). Because the swirler 47 draws airfrom inlets that are on a plane generally parallel to the swirl axis ZZ,the swirler 47 is sometimes described as being a radial swirler orhaving radial inlets (as opposed to as axial swirlers or axial inlets).

The swirler 47 further includes a forwardly extending swirler nozzle ora diverging outlet 51, which for convenience of description may bereferred to simply as cone 51 (although, the configuration may be morecone-like than a true geometrical cone). In an aspect of the invention,the cone 51 defines a divergent sidewall 61 positioned about swirl axisZZ, but which diverges from the axis YY along the forward axialdirection. The divergent sidewall 61 is shaped in a specificadvantageous manner, as further described below. The open center of theswirler 47 preferably corresponds with the opening in the end wall 37 sothat the cone 51 extends forwardly and outwardly in the combustionchamber 33 (see e.g., FIG. 4). In alternate embodiments, the cone 51 maybe independently constructed from and attached to the swirler plates 53.

In respect to Figures of specific embodiments provided herein, the cone51 or divergent sidewall 61 may be described as having or defining aninternal region or zone Zi radially inward of the cone 51 (also referredto as the fuel and air delivery zone Zi). Just forward of the end wall37, the diameter of the divergent sidewall 61 is reduced to define athroat area or throat 57 of minimum diameter. The fuel nozzle 49 extendsthrough the center opening of the swirler plates 53 and into the throat57. The fuel nozzle 49 is centered on the swirl axis ZZ to establish anannular gap 59 between it and the swirler plates 53. The nozzle 49 is,therefore, positioned to deliver an atomized fuel spray into theinternal zone Zi of the cone 51.

In accordance with the invention, a pathway of rotating air flow A1commences at the inlets between successive guide vanes 55 and rotatesabout the axis ZZ. While advancing radially inward, the air flow A1intensifies as the rotational path shortens and converges on the annulargap 59 and the swirl axis ZZ. This creates a low pressure area at thecenter of the swirler 47. Upon entry into the annular gap 49, the nowswirling flow presses against the center rim of the forward plate 55 andthen the base of the sidewall 61. The annular swirl flow A3 movesaxially forward, moving past the throat 57 and then, into the zone Zidefined internally (i.e., surrounded) by the cone 51. Centrifugal forcepresses the diverging, rotating flow to the sidewall where it forms anannular jet-like outflow A3.

As illustrated in FIG. 4A, operation of the fuel-air delivery system 45generates a local circular flow or circulation region CR in and aroundthe cone 51 and into the combustion chamber 33. The graphical diagram ofFIG. 6 is provided to further illustrate the fluid dynamics that arepresent and occurring directly in front of the swirler 47 and in thecone zone or region Zi, and the local circulation region LCR formedthereabout. The diagram provides a side profile of the zone Zi withindications representing the movement of fuel spray, air, and hot fluegases within the zone Zi of the divergent sidewall 61. A representationof the fuel nozzle 49 is provided at the graph origin, generally in thethroat 57 and along the swirl axis ZZ. The diagram indicates counterflowCF of hot flue gases directed back into the throat 57, a thin annularsection of swirling jet-like air outflow A3 from the swirler 47advancing forwardly along the divergent sidewall 61, and an area ofatomized fuel spray FS from a tip 63 of the fuel nozzle 49.

The profile of the sidewall 61 has the shape of the streamline indicatedby the bold curve SW. In preferred embodiments, the sidewall profile isdescribed by the relation, r/rmin=xs{x[2xs−(1+xs)x](1+xs)}−½, x=cos θ,and xs=cos θs. In this equation, r is the length of a line connectingthe axis-bottom intersection and a point on the sidewall, rmin is theminimum value of r, θ is the angle between the line and the axis, and θsis the θ value for a point located at the sidewall upper edge. Theparameters, rmin and θs, can be conveniently selected depending on theair flow rate and the fuel spray angle δ (see the angle between theswirl axis ZZ and the dotted line). Thus, a fuel spray angle δ 5 may beachieved that is sufficiently less than the sidewall angle θs to ensurethat the thin air flow A3 passes by the hot flue gas counterflow CF.

In accordance with the present invention, several operational featuresarise from the design of the swirler 47 and the sidewall profile. First,the surface of sidewall 61 exhibits relatively little or low drag due toits design as a stream surface. Secondly, the swirler 47 generates a lowpressure area, which can be largely attributed to a rarefaction near thethroat 57 generated by focused air rotation about axis ZZ. A strongsuction is generated at the throat 57 which draws hot flue gases passingin front of the swirler 47 and the local circulation zone LCR. Thissuction creates a hot counter flow-CF toward the throat 57. As FIGS. 4Aand 6 reveal, the counter flow CF occupies a wide area (diameter) acrossthe cone 51, which is indicative of the strength of the suction createdby the swirler 47 and allowed by the angle θ of the sidewall 61. Thestrong suction and resulting counterflow CF may also cause fuel dropletsto flow into back into the throat 87 and potentially past the nozzle tip63. To guard against escape and possible deposit of these counterflowingfuel droplets, air flow A2 is directed through the annular gap 59 toengage and divert the counter flow CF thereabout.

Furthermore, because the swirling jet outflow A3 is pressed to thediverging part of the sidewall 61 by centrifugal force, there is littleswirl in the center and in the hot flue gas counter flows CF. Withreference again to the diagram of FIG. 6, the counterflow CF efficientlytransports hot flue gases to the throat 57 and the tip 63 of the nozzle49. The hot flue gases heat fuel emitted by the fuel nozzle 49 into theregion between the swirl axis ZZ and the dotted line in FIG. 8B. The hotflue gas also heats the air flow A3, help evaporate liquid fuel dropletsand initiate combustion near the nozzle tip 63. The counterflows CF alsodecelerate the travel of the sprayed droplets, which increases theirresidence time in the hot environment and facilitates evaporation. Also,since swirl is nearly absent in the spray region, the droplets are notrapidly driven to the sidewall by centrifugal force and, therefore, donot deposit on the sidewall. Finally, the stagnant annular regionseparating the near-sidewall outflow and the near-axis inflow serveseffectively as a flame holder providing stable moderate-temperaturecombustion.

In operation, the combustion apparatus 7 according to the inventioninitiates a combustion process with multiple advantageous features. Inone aspect of the invention, such a combustion method is achievedutilizing a single combustion chamber for flameless combustion.

In a further aspect, a method of combustion according to the inventioninvolves the advantageous high-speed circulation of combustion fluids(air, fuel, and/or fuel-air mixture) inside the combustion chamber. Morespecifically, preferable operation of the combustion apparatus 7,according to the invention, establishes dual modes of circulation orfluid flow: a first mode entailing the revolution of fluid particlesaround the longitudinal axis YY (swirl) and a second mode entailingcirculatory meridional motion of the combustion fluids. As describedbelow, this dual mode of circulation enhances the mixing of air and fuelin the combustion chamber and helps achieve desired combustioncharacteristics and temperature profiles.

Advantageous Circulation in the Combustion Chamber

The simplified schematic of FIG. 7 illustrates the axial and circularflows (of air, fuel, other combustion constituents, and their mixtures)generated in the combustion chamber 33 according to the presentinvention. More particularly, FIG. 7 reveals two types of global axialflows induced in the combustion apparatus 7 according to the invention:circulatory flows generally centered about circulatory regions CR andflow-through (flows) in the flow-through regions FT, which exit thechamber 33 as exhaust. As discussed below in respect to FIG. 7A, thecirculatory meridional motion in the combustion chamber 33 is initiatedby centrifugal convection. Pressurized air introduced into the chamber33 is cooler than the interior part of the chamber 33. As this incomingair flows near the sidewall 35, its temperature increases and approachesthe flue gas temperature. An axial temperature gradient is thereforeprovided along the sidewall 35. This temperature gradient combines withswirl flow about the axis YY to drive meridional circulation within thechamber 33 (even with no flow-through). This driving mechanism furthercombines with the effect of combustion in the chamber 33 andflow-through (discussed further below) to induce high-speed circulatoryflows within the chamber 33.

Additionally, the applicants utilize the contribution of swirl-decaymechanisms in generating counter-flows (i.e., both the circulation andthe U-shape flow-through, in the combustion chamber). Generally,air-sidewall friction causes a pressure drop in the air flow in theaxial direction. Thus, the pressure at air inlet 43 is significantlyhigher than the pressure at the end of axial flow travel, near theproximal end wall 37. Pressure is also lower at the swirl vortex. Thus,pressure near the sidewall 35 at the proximal end is significantlygreater than the pressure at the axis YY (the swirl axis) near theproximal end wall 37. Finally, the pressure at the axis YY near thedistal end wall 39 is greater than the pressure at the axis YY at theproximal end wall 37. This is primarily due to the swirl rotationalspeed having decreased along the axial length of the sidewall 35friction and effecting less of a pressure drop at the proximal end. Theabove-described pressure gradients help drive the meridional motion andin particular, the advantageous turns and reverse flows made by fluidflow in the combustion chamber 33. These pressure gradients and swirldecay effects are also utilized in the embodiments of the presentinvention through strategic arrangement of the tangential and axial airinlets, as described below.

Referring first to the schematic of FIG. 7, high-pressure fresh air A0enters the combustion chamber 33 through the air inlet 43. Because theair inlet 43 is positioned tangentially to the sidewall 35 of thecylindrical combustion liner 33, the high velocity air inflow A0 intothe cylindrical chamber 33 is directed tangentially near the insidesurface of the sidewall 15 35 and generally transverse to thelongitudinal axis YY. This high velocity tangential inflow A0 inducesand drives a swirling motion (illustrated in FIG. 8) of the airparticles about the chamber axis YY. In preferred methods utilizing thecombustion apparatus 7 of FIGS. 1-5, this air inflow A0 is presented atan axial location physically near the exhaust opening 25 and exhaustflow E0 of the chamber 33. The desired swirl about the longitudinal axisYY also commences at this near-exhaust axial location. Notably, thedirect path between the air inlet opening 43 and the exhaust opening 25is relatively short—well below the value of the diameter of the chamber33 and possibly, slightly longer than its radius. This direct path isdescribed as being a “clear direct path” (i.e., free of any structuralbarrier obstructing or diverting a direct flow path), as opposed to anobstructed path (i.e., characterized by a combustion exhaust tube,baffle, or other structural barrier physically separating thepressurized air inflow from the exhaust flow).

The fresh air inflow A0 has, of course, a temperature that issignificantly less than that of the gases already inside the chamber 33,especially the hot flue gases. Thus, the constituents of this fresh airinflow A0 generally are of a higher density than the hot gases and othercombustion particulates. In the combustion chamber 33 of the invention,centrifugal buoyancy and centrifugal force act to push thehigher-density air radially outward. The effect of centrifugalacceleration on the air particles may be larger than that ofgravitational acceleration by four to five orders of magnitude. As aresult, even a small difference in temperature (and therefore indensity) causes stratification (until mixing and combustion togetherheat the incoming flow up to the flue gas temperature in the circulationregions CR). Since most of the incoming air initially flows in a thin,annular layer close to the sidewall 35, its axial velocity is lowcompared with that of the existing circulatory flows and the centralflow-through. The maximum axial velocity of the near-sidewall flow isestimated to be around one third of that of the near-axis flow. Therelatively low axial velocity of the near-sidewall air flow increasesits residence time, however, and thus, provides sufficient time for thepreheating, mixing and combustion of air. In preferred embodiments, theresidence time of the near sidewall air flow may be higher than themixing time by orders of magnitude, and its combustion time smaller thanthe mixing time.

Returning to FIG. 7, the swirling air inflow A0 generally advances fromthe air inlet 43 (the “cold” side of the combustion chamber 33) to theproximal end wall 37 of the combustion chamber 33 (the “hot” side of thecombustion chamber 33) primarily due to centrifugal convection. The flowlines in FIG. 7A isolate and illustrate the meridional motion orcirculation of the fluid mixture (air and fuel) inside the combustionchamber 33. The flow streams or flow lines are substantially symmetricabout axis YY in all directions and thus, only a one-half section of thechamber 33 is represented. As mentioned above, the flow lines A0advancing from the air inlet 43 are concentrated along the sidewall 35,well away from the center of the combustion chamber 33. Upon reachingthe region of the proximal end wall 37, the flow lines turn radially 20inward toward the axis YY and into the proximity of the fuel-air mixturedelivery system 45. From there, the flow lines again turn about ninetydegrees into the axial direction of the exhaust 25, thereby completing aU-turn. In this return air flow, the flow lines are directed generallycentrally in the combustion chamber 33 and alongside longitudinal axisYY.

As shown in FIG. 7A, the returning air flow along the longitudinal axisYY takes two different paths. A portion of the returning flow flowsthrough and out of the combustion chamber (via the exhaust 25). Thisflow-through portion FT is situated near the axis YY of the combustionchamber 33, and in general axial alignment with the exhaust 25. Anotherportion of the return flow is situated radially outward of theflow-through portion FT, but also directed axially toward the exhaust25. Before reaching the exhaust 25, the flow lines of this portion turn90 degrees and head radially outward. Then, before reaching the sidewall35, this outward flow again turns 90 degrees (a second U-turn) and inthe opposite axial direction, while engaging the freshly incomingpressurized air flow A0 into the combustion chamber 33. As shown in FIG.7A, the returning flow lines are situated radially inward of thesidewall 35 and the freshly incoming pressurized air A0 that flow alongthe sidewall 35. These flow lines, which are again directed axiallytoward the “hot” side of the chamber 33, represent full circulation ofgases in the combustion chamber 33. The region or pattern defined bythis meridional circulation is referred to herein as the circulatoryregion CR. As shown in FIG. 7, two circulating regions CR areestablished during operation of the combustion apparatus 7.

The high-speed circulatory flows generally consist of hot flue gasesmoving in the circumferential, axial, and radial directions. Notably,the circulatory flows are located downstream of the swirler 47 and thenozzle 49. The nozzle and swirler arrangement and orientation providefor the injection of atomized fuel into the circulatory region CR.Droplets of liquid fuel introduced into the region CR will evaporatequickly upon contact with the hot flow. Gaseous fuel introduced into theregion CR, on the other hand, will be quickly preheated and mixed by thehot, high-speed and turbulent flow.

In one aspect of the present invention, the circular flow describedabove and illustrated in FIGS. 7 and 7A interacts advantageously withthe freshly entering inflow A0 of pressurized air. As the freshlyentering air advances along the sidewall 35, this incoming air is heatedthrough contact and mixing with the hotter flue gases that are moving inthe circulatory regions CR. Fuel droplets injected by the fuel nozzle 49enter the hot flue gas region, revolve about the axis YY, and are alsopushed toward the sidewall 35 by centrifugal force. As the droplets movetoward the sidewall 35, flue gases in the circulatory region CR heat andthen cause the droplets to begin to evaporate. As the preheated air andfuel meet near the sidewall 35, combustion commences. The resultingoverheated combustion products move toward the chamber axis YY driven bycentrifugal buoyancy. These fresh combustion products mix with and heatthe flue gases in the circulatory region CR. A portion of the flue gasestravel along the longitudinal axis YY to the exhaust 25, while the restof the flue gases continue the circulatory motion described above.

The direction of cooler incoming air flows along the sidewalls 35provide yet another benefit. The cooler air flow provides a bufferbetween the combustion region and the sidewalls and end walls of theliner 31, and helps to maintain the sidewalls 35 at cooler temperatures.Such thermal protection allows for the use of lower-cost material forthe sidewall 35 and typically results in a more double and longerlasting sidewall 35.

FIG. 7A also represents the results of numerical simulations of thecircular flow schematically shown in FIG. 7. More specifically, FIG. 7Aillustrates the analytical solution of the Navier-Stokes equations for acompressible ideal gas. This solution describes a flow in a rotatingcylindrical container, in which wall temperature varies in the axialdirection. As described above, the gas swirls around the axis, advancesalong the sidewall 35 from the cold end wall 39′ to the hot end wall37′, turns toward the axis YY near the hot end wall 37′, flows along theaxis YY to the cold wall 39′, and then turns outward to the sidewall 35′near the cold end wall 39′. The flow described, which incorporates bothswirl around the axis YY and meridional circulation, is referred to ascentrifugal convection. During operation, swirl and an axial temperaturegradient are also generated in the combustion chamber 33 of the presentinvention. Accordingly, centrifugal convection is induced inside thecombustion chamber 33, particularly, inside the circulatory regions CRschematically shown in FIG. 7. The advanced solution also describes theadditional swirl decay mechanism of the circulation flow and takes intoaccount effects of the inflow and the exhaust in the combustor.

Double Spiral Swirl Promotes Fast and Fine Mixing throughout

In a further aspect of the invention, swirl generated in the combustionchamber 33 is characterized by an advantageous double-spiral geometricpattern. FIGS. 8A-8E provides three dimensional views of air and fluegas particle trajectories induced in the combustion chamber 33,according to the present invention. Trajectories Ta, Tb, and Tc followparticles moving inside one of the circulation regions CR. In moredetail, trajectory Ta follows a particle moving close to the center ofthe circulation region CR (see the inner closed curve Si in FIG. 7A)while trajectory Tc follows a particle moving along the circulationregion CR boundary. Trajectory Tb follows a particle moving betweentrajectories Ta and Tc. The other trajectories, Td and Te, areassociated with particles moving in the flow-through region FT.Trajectory Td follows a particle moving in the flow-through region FT,but close to the circulation region CR. Trajectory Te, on the otherhand, follows a particle initially moving close to the sidewall 35 ofthe combustion chamber 33 and then along the longitudinal axis YY towardthe exhaust 25.

For each of the trajectories in FIG. 8, an outer spiral So isestablished near the sidewall 35 while an inner spiral Si is establishedradially inward of the outer spiral So and closer to the axis YY. Thewavy and counter-flowing motion provided by this double-spiral geometrypromotes fast and fine mixing of air, fuel, and flue gas throughout theentire combustion chamber, thereby enhancing volume-distributedoxidation. Temperature readings at various remote locations in thecombustion chamber 33 revealed fairly well uniform temperaturedistributions throughout the chamber 33. This is further indication thatthe dual mode of circulation according to the present invention achievesefficient mixing of fluids in the combustion chamber during operation.

Comparison of trajectories Td and Te also reveals that a particle movingclose to the sidewall, (e), makes more revolutions around the axis YYthan the particle remote from the sidewall, (d). The particle close tothe sidewall 35 has, therefore, a lower axial velocity than that the oneremote from the sidewall 35. Furthermore, the particle close to thesidewall 35 has a longer residence time in the combustion chamber 33than the particle remote from the sidewall 35. As centrifugalstratification provides that the colder particles will be closer to thesidewall 35 than the hotter particles, the cold particles are providedsufficient time to heat up. Moving slowly along the sidewall 35, thecold particles are continually heated by the hot sidewall 35, by thehotter flue gases with which it mixes, and finally due to heat fromcombustion. Trajectory (e) in FIG. 8, which is typical for initiallycold particles, shows that a cold particle spends more than 90% of itsresidence time moving along the sidewall 35 and near the end wall 37.(Note also that the axial length of preferred combustion chambers islonger than its diameter (elongated combustion chambers), and oftensubstantially longer). The particle's travel along the axis YY (betweenend walls 37, 39) takes less than 10% of its residence time. Keeping inmind such behavior of the flow particles, an alternative embodiment ofthe combustion chamber is provided and described below.

Volume Dominance and High-Speed Circulatory Flows

An important feature revealed in FIGS. 7 and 7A is a circulatory regionCR that occupies about ⅔ of the volume of the combustion chamber 33. Theflow-through region F0 occupies only the remaining ⅓ of the chambervolume. Such volume dominance by the circulatory flow makes thecombustion stable even for a high-speed flow-through. Applicants haveobserved, for example, a stable combustion at an incoming air velocityexceeding 200 m/s.

The volume dominance and high-speed motion of the circulatory flowsprovide intense and fine mixing of incoming air with flue gases. Thecirculatory flows quickly heat up the incoming air up to theself-ignition temperature. The volume dominance and high temperature ofthe circulatory flows also provide intense preheating and evaporation(for liquids) of fuel injected by the nozzle 49 into the circulatoryflow regions CR. The fast and fine mixing results in uniformdistribution of both fuel and air in the entire combustion chambervolume. Therefore the fuel and air meet and combust everywhere in thechamber 33, i.e., volume-distributed oxidizing occurs.

The volume dominance, high speed and high temperature of the circulatoryflows also help to establish the circulatory regions CR as safe andefficient flame holders. Because the flow-through regions FT is pressedproximate the combustor sidewall 35 by centrifugal force and centrifugalbuoyancy, the flow-through streams cannot readily cause blow-out and/orcool down the circulatory flows. Furthermore, combustion uniformly heatsall of the constituents throughout the chamber 33 due to intense mixingand, in particular, maintains the circulatory flow at high temperature.Combustion also causes the through-flow and circulation flows toaccelerate and thus, maintain the circulatory flows at high-speed.

FIGS. 7 and 7A also illustrate that, near the exhaust 25 and distal endwall 39, the circulatory flow is turned outward to the sidewall 35. Thiscounter flow blocks what would otherwise have been a short-cut passageof entering air flow A0 directly to the exhaust 25. This flow featureacts in conjunction with centrifugal force to push the higher-densityincoming air flow A0 toward the sidewall 35. In one respect, these flowfeatures provide the flow barrier function exhibited by the combustionexhaust conduit discussed above. The results are that the flow lines arelonger, the residence time for air-fuel mixtures in the combustionchamber are longer, and a more complete combustion is assured.

Alternate Combustion Apparatus and Methods

FIG. 9 is an operational schematic representing operation of acombustion apparatus 107 in accordance with an alternative embodiment ofthe invention, wherein like reference numerals are used to indicate likeelements. Operation of the combustion apparatus 107 provides many of thesame advantages that are available with the earlier-described combustionapparatus 7 of FIGS. 1-5. The configuration of the elongated combustionapparatus 107 is substantially similar to that of the combustionapparatus of FIGS. 1-5, except for one structural variation: theprovision of an air inlet 171 into the cylindrical combustion liner 131adjacent the proximal end wall 137. In contrast to the earlier describedembodiment, the air inlet 171 is located remotely from the chamberexhaust 125. As with the earlier embodiment, the air inlet 171 ispositioned and configured to direct fresh air inflow A0 tangentiallyinto the cylindrical chamber 133. The fuel-air mixture delivery system145 and flue gas exhaust 125 are located substantially axially onopposite sides of the chamber 133. As before, operation of thecombustion apparatus 107 generates dual modes of circulation in thechamber: swirl about the longitudinal axis YY and meridional motion.

FIG. 9 also illustrates the meridional motion of the fluid flows in thecombustion chamber 107 during operation. Noting the influence of swirldecay mechanisms, the initial inflow A0, while drawn along the sidewall135, travels from the proximal side of the chamber 133 to the distal orexhaust side of the chamber 133 and gradually decreases in swirlvelocity. At the distal end wall 139, the flow lines turn inwardlytoward the axis YY (region of low pressure). Then, some of the flowlines turn and are directed in the reverse axial direction toward theproximal end wall 137. Some flow lines go out as flue gas exhaust E0through the exhaust opening 125. Notably, the flow-through flow lines(and flow-through regions, FT) are found along the side wall 135 andalong the distal end wall 139. Unlike operation of the earlier describedcombustion apparatus 7, the central core region near and about the axisYY in this embodiment is not occupied by flow-through flow lines, but bycirculating flow lines (and circulating regions, CR).

As compared with operation of the earlier-described combustion apparatus7, operation of this combustor 107 features a shorter passage length(the flow-through flow line from the air inlet 171 to the exhaust 25).Accordingly, the residence time of the particle in the flow-through lineis shorter. Seemingly, this feature would present a significantperformance disadvantage, especially considering the benefits providedby longer residence times as explained above in respect to thecombustion apparatus 7 of FIGS. 1-5. This alternate design does,however, provide its own unique and advantageous feature. As shown inFIG. 9, operation of the combustion apparatus 107 generates a largercirculation region CR than the earlier-described combustion apparatus 7.Now including the core region about the axis YY, the larger circulationregion CR occupies an even greater volume of the combustion chamber 133.

FIG. 9A provides a representation of the numerical flow simulationsschematically shown in FIG. 9 (similar to that provided by FIG. 7A). Thesimulations reveal circulatory regions CR inside the combustion chamber133 that occupy about ¾ of the interior volume, while the flowthroughregion FT now occupies only about ¼ of the interior volume. Theincreased dominance of the circulatory flow results in a highervolume-averaged temperature. Therefore, more thermal energy is availablefor heating water and other diluting species in low-grade fuels. Thismakes the combustor design illustrated in FIG. 9 well suited for burninglow-grade fuels, such as glycerol.

FIG. 10 depicts a simplified schematic of yet another embodiment of acombustion apparatus according to the invention. In this schematic, onlyone-half of the combustion apparatus 207 and a combustion chamber 233 isrepresented. The combustion apparatus 207 is equipped with twotangential air inlets 243 a, 243 b located at opposite axial ends of thecombustion chamber 233. High pressure, high velocity air enters thechamber 23 at each inlet 243. Both air inflows A1, A2 travel near thesidewall 235, with the air inflow A1 at the exhaust end moving towardthe proximal end and the air inflow A2 at the proximal end moving, inthe opposite direction, toward the distal or exhaust end. Midway acrossthe axial length of the chamber 233, the two air flows A1, A2 collide,mix, and then turn inward toward the chamber axis YY. Near the axis YY,the resulting air flow turns again and advances toward the exhaust 225.

FIG. 10A represents the results of numerical simulations of the internalflows inside the combustion apparatus 207 during operation, similar toFIG. 7A in respect to the combustion apparatus 7 of FIGS. 1-5. Operationof the combustion apparatus 207 reveals two circulatory regions, CR1 andCR2, with beneficial features similar to those circulatory regions CRdescribed above. One of the circulatory flows or regions, CR1, islocated in a dilution zone, while the other, CR2, is located in thecombustion zone. The enhanced mixing in the combustion zone helpsprovide stable and low-emission combustion. The enhanced mixing in thedilution zone helps finalize and complete the combustion of fuelrendering species concentrations in the exhaust flow more uniform.

The provision of a second inlet 243 b near the proximal end wall 237advantageously provides for a higher speed, cooler flow-through at the“hot” proximal end. The local circulation region LCR and combustion zoneare present at the proximal end. In the previous configuration, thesidewall 235 at the proximal end experiences higher temperatures due toits proximity to the combustion zone and also, because the inlet airflow A0 gets hotter and slows as it travels axially along the sidewall35 before arriving at the proximal end. The higher speed, cooler airinflow A2 provides a more effective cooling fluid flow. Additionally,the addition of higher speed swirl flow near and in contact with thelocal circulation zone LCR and near the fuel spray from the nozzle 149enhances mixing and heating of combustion constituents. Moreparticularly, the addition of higher speed swirl flow at the proximalend helps to generate counter-flows (flows in opposite directions),thereby promoting the occurrence of swirling vortices and Karman eddies.These eddies facilitate the desired fast and fine mixing of combustionconstituents.

Burner

The simplified illustration of FIG. 11 provides an alternativecombustion apparatus according to an alternative embodiment of theinvention. The combustion apparatus in this embodiment is in the form ofa burner 307. The burner 307 utilizes a fuel-air delivery system 345that is substantially similar to the system 145 described in respect toFIGS. 3-6. In this application, the burner 307 is not confined within acombustion liner and does not exhausts into a transition piece, turbine,or other device. The burner 307 is particularly suited for use in directheating applications.

As before, the fuel-air delivery system 345 includes a fuel nozzle 349,a radial air swirler 347, and a swirler nozzle or cone 351 extendingforwardly along a swirler axis ZZ. The cone 351 further includes adivergent sidewall 361 having an advantageous profile as describedpreviously. In this alternate configuration, the air swirler 347 andfuel nozzle 349 are supported within a casing 381. More specifically,the swirler 347 is mounted on the inside wall of a flange or backplate383, such that the cone 351 extends outward through a central opening ofthe backplate 383. As second backplate 385 encloses the casing 381 todefine an air chamber 385. As shown in FIG. 11, an air inlet 387 extendsthrough the casing 381 to supply pressurized air to the air chamber 385.

During operation, an air inflow A1 is drawn by radial guide vanes 355 ofthe swirler 347. The guide vanes 355 generate a high speed rotationalinternal flow that converges on the center of the swirler 347 andadvances forwardly therefrom into a throat 357 of the swirler 347 andalong the divergent sidewall 361 of the cone 351 (as discussedpreviously). Additional air flow A2 is drawn through an annular gap 359around the nozzle 349 and passed into the throat 385 to engage anycounter flowing fuel droplets drawn back into the swirler 347 or throat385. As also described earlier, a jet-like air swirl flow A3 generatedby the swirler 347 is pressed thinly and annularly against the sidewall361, while and fuel spray is directed outwardly by the nozzle 349 fromthe area of the throat 385. Advantageously, the angle of the fuel sprayis designed to be less than that of the sidewall 361 so that the thinjet-like layer of air swirl A3 near the sidewall 361 is clear from theextent of the fuel spray.

As illustrated in FIG. 11, the fuel-air delivery system 345 generates alocal circulation region LCR in front of the cone 351. The localcirculation region LCR is characterized by hot gas counterflow CF andeddies generated by oppositely-directed (counter) flows. Accordingly,the local circulation region LCR provides fast and fine mixing of air,fuel, and species concentrations.

The simplified schematic of FIG. 12 illustrates yet anothersingle-chamber combustion apparatus 407 according to the presentinvention, and the beneficial modes of circulation generated therein. Inthis variation, the combustion apparatus 407 includes a combustor liner431 that is fitted with a diaphragm 477. The diaphragm 477 isessentially formed by the introduction of circumferential baffles 479 inthe combustion chamber 433 and at a desired axial distance from theproximal end wall 437 (of the combustion chamber 433). An additional endwall 479 is added rearward of the proximal end wall 437 to create acylindrical air space 409 dedicated to the fuel-air delivery system 445.The diaphragm 477 separates the combustion chamber 433 into a maincombustion chamber 433 a and a pre-chamber 433 b. The fuel-air deliverysystem 445 is positioned to extend and direct primary air and fuel sprayinto the prechamber 433 b.

In this embodiment, the combustor liner 431 is equipped with twopressurized air inlets 443. A tangential air inlet 443 a is located nearthe exhaust 425 as before and a second tangential or radial air inlet443 b is located in the cylindrical air space 409. This second air inlet443 b supplies primary air A1 to the fuel-air delivery system 445.Independent of the first air inlet 443 a, this dedicated inlet 443 a maybe equipped with the required valves and controls to allow independentregulation of the primary air A1 feed to the delivery system 445.Specifically, the primary air fed to the swirler 447 may be controlleddirectly and independently of the air inflow A0 utilized in thecombustion chamber 433.

During operation, the combustion apparatus 407 generates, in addition toswirl about the longitudinal axis YY, global meridional circulationsimilar to that described in respect to combustion apparatus 407. Anadditional or local meridional circulation is also generated, however,local to the pre-chamber 433 b. As illustrated in FIG. 11, a portion ofthe flow along the distal side of the baffles 479 in the main combustionchamber 433 a is diverted into the prechamber 433 b to form circularflow (or counterflow) region CR2. This circulatory region CR2 helps coolthe prechamber 433 b and advantageously interacts with local circulationregions LCR. Furthermore, the counterflow presented by this circulatoryregion CR2 helps in drawing hot flue gases into the local circulationregions CR2 and creating the desired counterflow CF therein. Thecounterflow also help to generate Karman eddies, which, as discussedpreviously, helps promote fast and fine mixing of combustionconstituents.

The diaphragm 477 also helps to minimize the effect of increased airinflow A0 on the local circulation regions LCR. In particular, thebaffles 479 help to mitigate the effects of higher inflows and preventblow out in the local circulation region LCR. Accordingly, modes ofoperation requiring higher rate of air inflows may be achieved by thecombustor 407 without compromising the performance of the fuel-airdelivery systems 445 and local circulation regions LCR. FIGS. 13-14depict yet another combustion apparatus 507 according to an embodimentof the present invention. The combustion apparatus 507 employs many ofthe same components and provide many of the same operational features asearlier described embodiments. Referring first to FIGS. 13A-13D, thecombustion apparatus 507 includes an outer housing 513 having a proximalend wall 517 and a distal or exhaust end 519, both of which arepreferably aligned about a longitudinal axis YY. As best shown in FIGS.13A and 13B, a cylindrical air duct or casing 589 wraps about the outerhousing 513 near the exhaust end. The casing 589 further includes an airinlet pipe 527 for delivering high pressure air from an externalcompressor or equal. The outer housing 513 is preferably a cylindricalbody with flanged proximal and distal ends. As described in earlierembodiments, the proximal end generally provides receipt of a fuelsupply while the distal or exhaust end communicates hot flue gases to aturbine or other required component. The outer housing 513 in thisembodiment receives five individual fuel supply pipes 521 at theproximal end wall 517. Four of the fuel pipes are equally spaced fromand surrounds the fifth fuel pipe 521, which is preferably centeredabout the axis YY.

The combustion apparatus 507 further includes a cylindrical combustorliner 531 and a slightly conical transition piece 587 attached to thecombustor liner 531. As shown in FIG. 13D, the transition piece 587 ispositioned about the longitudinal axis YY and attached to a distal endwall 539 of the combustor liner 531. The transition piece 587 isequipped with a conical end wall 599 situated at the open end to directexhaust gases to an annular exhaust opening 599 a. The combustor liner531 is sized relative to the outer housing 513 to create a gap orannulus 541 therebetween. As shown, for example, by FIG. 13D, theannulus 541 extends from the transition piece 587 all the way to theproximal end wall 517. The air inlet casing 589 communicates with theannulus 541 to supply pressurized air throughout the extent of theannulus 541 and about both the liner 531 and the transition piece 587.Referring now to FIG. 14A-14C, the combustor liner 531 has asubstantially closed proximal end wall 537, a substantially open distalor exhaust end wall 539, and a sidewall 535 extending axially 10therebetween. The sidewall 531 defines, at least partly, a cylindricalcombustion chamber 533, according to the present invention. Thecombustor liner 531, in this variation of the invention, is equippedwith a pair of circumferential air inlets 543 a, 543 b, as opposed to asingle opening in the sidewall 531. The air inlet openings 543 a, 543 bare provided by plurality of radial guide vanes 593 circumferentiallypositioned about the proximal and distal ends of the combustor liner531. A first air inlet 543 a is positioned near the chamber exhaust 525,as with previously described embodiments. The second air inlet 543 b ispositioned near the proximal end wall 537.

As shown in the Figures, the two air inlets 543 a, 543 b may havesubstantially the same configuration. Each air inlet 543 a, 543 bprovides a set of radial guide vanes 593 arranged about the periphery,with each vane being positioned angularly to direct swirling air flowtangentially (not radially) into the combustion chamber 533. Theconfigurations of the two air inlets 543 a, 543 b differ, however, inthat the direction of the guide vanes 593 for one inlet is generallyclockwise while those of the other inlet are counter-clockwise. Thus,the directions of tangential air flows downstream of the air inlets 543a, 543 b and the swirl flows about axis YY generated thereby, are alsoin opposite rotational directions (clockwise or counter clockwise) andwill collide and mix midway across the sidewall 535.

FIGS. 14A-14C also show a backplate or flange 595 placed adjacent theproximal side of the circumferential air inlet 543 b. The backplate 595conveniently provides support for a fuel-air mixture delivery system545′ of the combustion apparatus 507. In a further aspect of the presentinvention, the fuel-air delivery system 545′ actually includes fiveseparate fuel-air mixture delivery systems 545 or, put in another way,five separate air swirler 547-fuel nozzle 549 combinations for directingthe desired fuel and air into the combustion zone. Individually, each ofthe delivery systems 545 is configured substantially the same as thefuel-air delivery system 45 described in respect to the combustionapparatus 7 of FIGS. 1-3. Each fuel-air delivery system 545 includes aswirler 54 having a swirler nozzle or cone 551 extending into thecombustion chamber 533 and a fuel nozzle 549 extending through the airswirler 547 to a throat 557 or within the cone 551. As best shown inFIG. 14D, in a preferred arrangement, a first delivery system 545 issituated centrally on the back plate 595 and generally about thelongitudinal axis YY. The remaining four delivery systems 545 are spacedoutward from and about the first delivery system 545 (this alsodetermines the relative positions of the cone 551 and local circulationregions LCR generated in the combustion chamber 533). As shown in theside views of FIGS. 14B and 14C, the first or center delivery system 545is preferably raised from the back plate 595, so as to extend axiallyrearward of the other four delivery systems 545. In this way, theswirler 547 of the center delivery system 545 is exposed to primary airflow from the annulus 541 (and not blocked by the other swirlers 547).

In this embodiment, two igniters 597 are provided and positioned oneither side of the center fuel-air delivery systems 545. The igniters597 extend into the combustion chamber 533 at an axial positionproximate the rim of the cones 551. As discussed previously in respectto the fuel-air delivery system 145, each of the systems 545 generates alocal circulation region LCR in front of and within each cone 551 (seee.g., FIGS. 4A and 6). Each of the local circulation regions LCR has thefeatures and properties discussed previously in respect to FIGS. 4A and6. Among other things, the local circulation regions LCR provideeffective flame holders and quickly heats and/or evaporizes fuelinjected by the nozzle 549.

The simplified flow representations (and their discussion) in FIGS. 10and 10 a are applicable and indicative of the flows and meridionalmotion that are induced in the combustion chamber 533 of thisembodiment. The unique configuration of the combustion apparatus 507translates to beneficial features in the flows in the combustion chamber533.

During operation of the combustion apparatus, the combustion chamber 533features two annular regions of high speed axial flow. The first is anannular region near the liner sidewall 535 and the other is located nearthe axis YY. These two regions of high speed flow is separated by anannular region of counterflow (in the portion of the chamber 533 nearthe fuel-air delivery system 545) or by lower-speed co-flow (near themiddle of the chamber 533). In addition, the similar counterflow and thelow-speed co-flow are located near the axis YY. The instability of thiscomplex flow, having multiple shear layers, generates turbulentKarmantype eddies densely packed throughout entire combustion chamber533. The presence of largescale eddies and small-scale turbulence resultyet again in fast and fine mixing of air, fuel, and flue gases, therebypromoting stable and complete combustion with low level of harmfulemission. FIGS. 15A and 15B are provided to illustrate the additionaland enhance flow dynamics generated by the multiple swirlerconfiguration of FIGS. 14 and 15. In particular, the utilization ofmultiple fuel-air mixture delivery systems 545 translates to multiplelocal circulation regions LCR and multiple regions of counterflows CF.As discussed above, the presence of counterflows CF in the operation ofthis combustor apparatus 507 provide for the desirable generation ofswirl vortices or fine scale Karman vortices. Specifically, thesevortices Vx are generated in the transition regions between counterflowCF.

FIG. 15A is front plan view of the area of the fuel delivery system 545′near the proximal end of the combustion chamber 533. As shown, a thinjet-like air flow A3 is directed outward on the divergent sidewall 561of the swirler cone 551. This high speed swirling flows A3 arecharacteristic of each of the local circulation regions LCR, and arepresent near the periphery of the region LCR. The peripheries of thevarious local circulation zones LCR encroach on other peripheries, inrespect to the central fuel-air delivery system 545 and each of the foursurrounding fuel-air mixture delivery systems 545. Thus, there existcounter flowing swirling air flows A3, and in the transition regionbetween these, desirable vortices Vx form (as shown in FIG. 15A).

Now turning to the side or profile view of FIG. 15B, swirl vortices Vxin the longitudinal planes are also generated. As mentioned previouslyin respect to FIG. 4A, the hot flue gas counterflows CF are directedback to the area of the fuel nozzle 549, while the thin jetlike swirlingair flow A3 presses forwardly along the divergent sidewall 561.Furthermore, the counterflow CF drawn toward the nozzle 549 also reversedirection and flow outward at certain places. Thus, there are transitionregions in and near the region of the cone 551 at which inward flow andoutward flow are found. Fine scale Karman vortices are advantageouslydeveloped in these transition regions.

As further shown in FIG. 15B, there are transition regions outside ofthe cone 551 and/or the local circulation regions LCR. Outward flowsnecessarily extend out of or escape these regions. As discussedthroughout this disclosure, organized axial flows are generated in thecombustion chamber 533. Some of these axial flows are found in or nearthe proximal end and meet or flow aside the outward flows. Transitionregions and Karman vortices occur, for example, near the sidewall 535and axially forward of the cones 551.

Thus, in a preferred combustion apparatus and method of combustionaccording to the invention, a combustion liner is provided having atleast one air injection inlet tangentially positioned to inducehigh-speed swirl about the chamber axis. The combustion liner is furtherconfigured, and the inlet port(s) is properly positioned, so as toinduce a desired high-speed meridional motion inside the chamber.Relatively large circular flow regions are generated and interact withflow-through regions, which include regions along the sidewalls. Morepreferably, at least one air-fuel swirler is provided for generating anarrow annular jet and a wide suction flow. The resulting multiple shearlayers, densely packed Karman-type eddies, fine-scale turbulence, andparticle trajectories of double-spiral geometry cause fast and finemixing of air, fuel and flue gases as well as extremely uniformtemperature distribution. The large circulation/flow-through volumeratio and high-speed circulation provide stable combustion, rapidpreheating and mixing of injected fuel, and uniformly occurringoxidation in the entire combustion chamber or combustion liner volume atoptimal temperature with minimum harmful emission.

FIG. 16A provides an exhaust end view of an alternate combustionapparatus 607, according to the invention The combustion apparatus 607of this embodiment employs an arrangement of four circumferentiallyspaced-apart air inlet pipes 627 (for pressurized air supply) thatcommunicate with a housing 613. The housing 613 extends over atransition piece 687 and is spaced therefrom by way of annulus or gap641. Pressurized air entering the annulus 641 reaches, therefore, theoutside of the transition piece 687 (in addition to the combustionchamber and the outside of the liner).

The transition piece 687 is provided for engagement with a turbine orother suitable mechanism. The transition piece 687 has a diameter thatincreases gradually from the end at which it engages a combustion liner631 and receives exhaust gases, to an exhaust opening 605 downstream. Asshown in FIG. 16B, the front of the transition piece 687 issubstantially occupied by a hollow conical end wall 699 (and a cap 673spaced just axially inward of the end wall 699). The end wall 699 issized smaller than the housing 613, so that a circumferential gap 671 isprovided therebetween. The gap 671 presents an annular exhaust opening671 for the escape of combustion chamber exhaust gases. Because of itslocation in the direct path of hot exhaust gases, the end wall 699 maybe exposed to and experience extremely high temperatures. Accordingly,in some applications, the end wall 699 may be made of or supplementedwith materials capable of withstanding high heat conditions. In oneaspect of the invention, the combustor apparatus 607 is equipped with anintegrated cooling system for reducing the effect of high temperatureson the end wall 699 and other components of the transition piece 687.

In this embodiment, the hollow end wall 699 is configured with aninterior hollow or cavity 675. At about the axis YY, an axiallyextending port 677 is provided from the cavity 675 to the outside of theend wall 699 (inside of the transition piece 687). The cap 673 isattached to the end wall 699 by a short rod 685 (near the port 677) andis centered on the axis YY.

Furthermore, the end wall 699 is supported in place by four short tubes695 that extend from the housing 613. The tubes 695, which are open tothe annulus 641 on one end and the cavity 675 on the other end,communicate relatively cool air from the annulus 641 to the end wall699. Air flow directed into the cavity 675 converge on the axis YY andthen exit through the port 677. The pressurized air spills into theannular gap between the cap 673 and the end wall 699, and then deflectedby the cap 673. From there, the deflected air flow moves outward to theexhaust opening 671 along the inside surface of the end wall 699. Inthis way, air flow convectively cools the outside, as well as theinside, of the end wall 699.

In one aspect of an invention provided in the present disclosure, acombustor features a single combustion chamber that receives fuel andair (or other oxidizer) and initiates combustion. More specifically, thecombustor employs a combustion container having an elongated combustionchamber and a tangential air inlet into the chamber that induces swirlabout the chamber axis and meridional circulation, thereby effectingadvantageous mixing and preheating. Furthermore, the combustioncontainer is preferably configured such that the tangential air inlet islocated proximate the chamber's exhaust (without any structural barriersdirectly between the inlet and the exhaust). FIG. 17A provides asimplified representation of such a combustion container (withindications of swirl flow omitted). Key structural elements representedand noted in the Figure include: a single, elongated combustion chamber;a tangential air inlet (for swirl); and the air inlet is proximate theexhaust.

An important additional element of a preferred combustor's design is theinclusion or incorporation of a casing that substantially encloses thecontainer but is spaced outwardly from the combustion container tocreate a gap or annulus. This annulus serves to divert and direct airflow about the outside of the combustion container and\or to a fuel-airdelivery system of the chamber. In this way, the annulus airflow servesto cool the combustion container and re-direct heat and energy back tothe combustion process. This preferred embodiment of the combustor witha “Casing and Annulus for Air Flow Cooling and Energy Recapture” is alsoillustrated in the combustors of FIGS. 1 and 13-16, but may also beincorporated and adapted with the combustors described in respect toFIGS. 7 and 12.

To elaborate, FIG. 17B provides a simplified illustration of a combustorhaving, among other elements, a casing (C), an air flow annulus (A), anda combustion container (L) defining a combustion chamber (Ch). As theair flow is directed toward the proximate end and in the vicinity of thefuel-air delivery system (FA), it cools the sidewalls of the container(L) through convective (and conductive) heat transfer, which, in turn,facilitates heat transfer between hot gases inside the combustor chamber(Ch) and the sidewalls. As a further result, the air flow through theannulus is heated. The air flow and the heat loss (from the combustor)captured by it is directed back to the proximate end, and serves thefuel-air delivery system (FA) with a hotter air supply. In this way andin accordance with one aspect of the invention, a significant amount ofthe heat loss through the sidewalls is re-circulated into the combustionchamber (Ch).

In the drawings and specification, there have been disclosed a typicalpreferred embodiments of the present invention, and although specificterms are employed, the terms are used in a descriptive sense only andnot for purposes of limitation. The present invention has been describedin considerable detail with specific reference to the illustratedembodiments. It will become apparent, however, that variousmodifications and changes can be made within the spirit and scope of theinvention as described in the foregoing applications. For example,various components and systems described herein may be utilized indifferent combustion applications or in different combinations andconfigurations.

What is claimed is:
 1. A combustion apparatus comprising: a generallyelongated combustion container having a longitudinal axis, a proximalend, an exhaust end spaced axially forward from the proximal end,proximate end wall, an exhaust end wall, and an all-around sidewallextending between the end walls and about the longitudinal axis, the endwalls and sidewall substantially defining a combustion chamber; acombustion chamber exhaust positioned on the exhaust end; a deliverysystem positioned to direct fuel into the combustion chamber forcombustion; and an air inlet located generally tangentially on thesidewall to direct air flow generally tangentially into the chamber andinduce swirl about the longitudinal axis.
 2. The combustion apparatus ofclaim 1, wherein the air inlet is positioned forwardly of a longitudinalaxis midpoint of the chamber such that the tangentially directed airflow into the chamber commences a swirl flow axially proximate theexhaust and such that the swirl flow advances axially therefrom towardthe proximal end.
 3. The combustion apparatus of claim 1, wherein theexhaust includes an exhaust opening located on the exhaust end wall, theair inlet is located on the sidewall axially proximate the exhaustopening, and the delivery system is located on the proximal end wall toinitiate combustion in the proximate end of the combustion chamber. 4.The combustion apparatus of claim 3, wherein the combustion container iscylindrical and is configured such that a distance of a clear directpath between the air inlet and the exhaust opening is less than adiameter of the combustion container.
 5. The combustion apparatus ofclaim 1, wherein the air inlet includes a plurality of tangentiallydirected radial guide vanes arranged circumferentially about thesidewall.
 6. The combustion apparatus of claim 1, further comprising anair supply; and an outer casing spaced circumferentially outward of andabout the combustion container to define an annulus between thecombustion container and the outer casing, the outer casing furtherincluding an outer air inlet fluidly communicating the air supply withboth the annulus and the air inlet of the combustion container.
 7. Thecombustion apparatus of claim 1, wherein the delivery system includes anair swirler positioned to express an annular air swirl into thecombustion chamber at the proximate end and includes a radial inlet, aswirl chamber having an outlet with a swirl axis that is substantiallyparallel or coincident with the longitudinal axis of the combustionchamber, and a swirl nozzle outlet extending axially forward about theswirl axis into the combustion chamber, the swirl nozzle outlet defininga fuel and air delivery zone radially internal thereof.
 8. Thecombustion apparatus of claim 7, wherein the air swirler nozzle includesa base portion including a swirl chamber for receiving air flow and anaxially diverging outlet extending forwardly of the base for expressingan annular swirling air outflow.
 9. The combustion apparatus of claim 7,wherein the fuel-air delivery system is a fuel-air delivery system thatincludes a fuel nozzle directed axially into the air nozzle, the fuelnozzle including an outlet tip positioned for directing fuel into aregion defined internally by the nozzle outlet.
 10. The combustionapparatus of claim 9, wherein the air swirler has a longitudinal swirlaxis and an axial opening about the swirl axis, the swirl axis beingaligned with an axis of the nozzle outlet, and wherein the fuel nozzleis directed through the axial opening and the radial inlet is configuredto deliver a swirling air flow about the swirl axis, and wherein theaxial opening defines an annular gap about the fuel nozzle, the airswirler being configured to receive air flow though the annular gap andto a region of the nozzle outlet about the nozzle tip.
 11. Thecombustion apparatus of claim 1, wherein the combustion chamber includesa diaphragm dividing the combustion chamber into a dilution region and alocal combustion zone proximate the proximate end wall, the diaphragmincluding a partial barrier wall extending into the chamber generallytransversely to the longitudinal axis.
 12. The combustion apparatus ofclaim 1, wherein the delivery system includes an air swirler and fuelnozzle, the apparatus further comprising a supply air inlet in directfluid communication with the delivery system, the combustion containerbeing further configured to separate air inlet flow into the combustionchamber from supply air flow to the delivery system.
 13. The combustionapparatus of claim 12, further comprising an air chamber adjacent and influid communication with the supply air inlet and the fuel-air deliverysystem, the air chamber being separate from the combustion chamber andthe air inlet thereto.
 14. A method of combustion comprising the stepsof: providing an elongated combustion container having a longitudinalaxis, a pair of axially spaced apart end walls generally defining aproximate end and a distal end, a sidewall extending between the endwalls, and an exhaust opening in the distal end; delivering fuel intothe chamber at the proximal end; introducing tangential air flow intothe combustion chamber to induce swirl flow about the longitudinal axis,whereby the swirl flow further induces meridional circulation in thecombustion chamber; including circulatory regions and flow throughregions exiting the exhaust opening; and initiating combustion in thecombustion chamber including exhausting hot gases through the exhaustopening.
 15. The method of claim 14, wherein during the step ofintroducing tangential air flow, the swirl flow further inducesmeridional circulation including circulatory regions and flow throughregions exiting the exhaust opening.
 16. The combustion method of claim14, further comprising the steps of: positioning an air swirler in theproximate end whereby a swirl axis is parallel or coincidental with thelongitudinal axis of the combustion chamber and a swirler outletincludes a sidewall that extends axially forward into the chamber anddefines an outlet zone radially internal thereof; generating a localcirculation region in the proximate end, including generating a swirlingflow about the swirler axis such that suction is generated at the swirlaxis and the swirling air flow is expressed outwardly and annularlyalong the sidewall and directing fuel spray into the outlet zone,whereby the fuel spray is separate from the annular air swirl andwhereby a counterflow of hot gases from the combustion chamber is drawninto the outlet zone by the swirl suction to substantially vaporize fueltherein.
 17. The combustion method of claim 16, wherein the step ofintroducing tangential air flow further induces circulated meridionalmotion of combustion fluids said method further comprising delivering aliquid fuel spray at the proximate end and an annular swirling air flowabout the fuel spray, whereby the swirling flow diverges axially outwardaway from the fuel spray and a suction is generated to induce agenerally axial counterflow radially inward of the annular swirlingflow, and whereby the counterflow includes hot gases from the combustionchamber that substantially vaporizes fuel droplets from the liquid fuelspray.
 18. The combustion method of claim 17, wherein the annularswirling air flow and the generally axial counterflow generates a localcirculation region in the proximate end.
 19. The combustion method ofclaim 18, wherein the meridional circulation includes both globalcirculation regions and flow through regions in the combustion chamber,wherein the flow through regions are concentrated along the sidewall andabout the longitudinal axis to exit through an exhaust opening on thedistal end wall and the circulation regions are surrounded by the flowthrough regions and interact therewith.
 20. The combustion method ofclaim 19, wherein the step of introducing tangential air flow includesintroducing the tangential air flow proximate the exhaust opening,whereby swirl flow and flow through regions commence in the distal end.21. A fuel and air delivery system comprising: a radial air swirlerhaving a swirl chamber positioned about a swirl axis, a radial inlet forintroducing rotational air flow into the swirl chamber, and a centralopening positioned to receive swirling flow from the chamber; and a fuelnozzle directed axially through the central opening of the swirler; andwherein the air swirler further includes a nozzle outlet in fluidcommunication with the central opening and having an all aroundforwardly diverging sidewall for directing a diverging annular swirlflow outward.
 22. The system of claim 21, wherein the sidewall definesan outlet zone internal thereof, the fuel nozzle being positioned todirect a fuel spray into the outlet zone.
 23. The system of claim 21,wherein the fuel nozzle and the sidewall are configured such that thefuel nozzle directs a spray angle relative to the swirl axis that isless than a sidewall angle relative to the swirl axis, such that thefuel spray is spaced inwardly of the annular swirl flow along thesidewall.
 24. The system of claim 21, wherein the central openingdefines an annular gap between the fuel nozzle and the swirl chamber,the annular gap being configured to pass an axial air flow into theoutlet zone, and wherein the air swirler includes a throat defined by areduced diameter area of the sidewall, the air swirler being operable togenerate a low pressure area about the throat such that a counterflow isdrawn toward the throat.